JP3420904B2 - Lead wire loop forming method in wire bonding apparatus - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a lead wire loop in a wire bonding apparatus. In a wire bonding apparatus, a gold wire of about 20 to 38 μmφ is usually used as a lead wire connecting a pad (electrode) on a semiconductor chip and a lead of a lead frame. The loop shape of the lead wire connecting the pad and the lead affects the product quality. The loop shape is determined by the mechanical properties of the gold wire used, the supply amount, the movement trajectory of the capillary during bonding, etc. Is done. Among these, the movement trajectory of the capillary has an important influence on the loop shape. A method of forming a lead wire loop in a conventional wire bonding apparatus will be described with reference to FIGS. FIG. 2 is a movement locus diagram of a capillary during wire bonding, FIG. 3 is a loop shape diagram when the supply amount of the gold wire is about the same as the loop length, and FIG. 4 is a case where the supply amount of the gold wire is longer than the loop length. It is a loop shape figure. In the conventional wire bonding apparatus, as shown in FIG. 2, the capillary 1 is slightly lifted after a gold wire (not shown) is bonded to the first bond point (pad) 2 and then pulled up. After a slight distance is pulled back in the opposite direction to the second bond point 3 at this position (hereinafter, this operation is referred to as “reverse operation a”), the first bond point 2
Is raised to a loop-up point 4 almost immediately above (this operation is hereinafter referred to as “loop-up operation b”). Further, from the loop-up point 4 to the second bond point 3
Toward a certain point, for example, a circular arc having a radius r about the first bond point 2 as shown in the drawing, and moving (hereinafter, this operation is referred to as “loop-down operation c”).
A gold wire is bonded to the second bond point 3. When the capillary 1 is moved along a locus as shown in FIG. 2, the loop shape of the gold wire to be formed changes as follows according to the supply amount. That is, FIG. 3 shows a loop shape diagram when the supply amount of the gold wire 5 is made the same as the loop length, and the capillary 1 is on the reference arc d formed by the loop-down operation c (see FIG. 2). Therefore, the supplied gold wire 5 is always pulled. For this reason, the loop shape finally formed becomes a shape in which the bent wire 6 of the gold wire 5 formed by the reverse operation a (see FIG. 2) is extended, and a sufficient loop height cannot be obtained. FIG. 4 also shows that the supply amount of the gold wire 5 is bent.
The shape of the loop is shown in the case where it is lengthened to the extent that it does not break. The loop shape at this time can maintain the shape of the bent portion 6 because the extra gold wire 5 is supplied. The straight line portion following the bend 6 hangs down, and a sufficient gap cannot be formed between the gold wire 5 and the chip edge. As described above, in the case of the conventional loop forming method, the loop forming ability is limited, and it is difficult to cope with a wide variety of semiconductor devices. The present invention has been made to solve such a problem, and an object of the present invention is to provide a loop forming method in a wire bonding apparatus that is excellent in loop forming ability and can cope with a wide variety of semiconductor devices. . In order to achieve the above object, according to the method of the present invention, after bonding a lead wire to the first bond point, the capillary is lifted slightly to perform a reverse operation, and then a loop is performed. In a method for forming a lead wire loop in a wire bonding apparatus that is moved along a reference arc from the loop-up point to the second bond point after being pulled up to the up point, the loop-up point and the second bond point are connected. A step point is set at an appropriate position in the middle of the reference arc and at an appropriate position inside the reference arc, and the step point and the loop-up point are formed around the arbitrarily set first center point. Move the inside of the reference arc along the first arc connecting the step point and the loop-up point, and between the step point and the second bond point , Along the second arc connecting the step point and the second bond point formed around the arbitrarily set second center point, from the inside to the outside of the reference arc to the second bond point It is characterized by being moved to. In the case of the construction as described above, since the capillary passes inside the reference arc from the loop-up point to the step point, the lead wire is not pulled and the bending fold does not extend, Further, since the capillary reaches the second bond point from the inside of the reference arc through the outside between the step point and the second bond point, the supplied lead wire can be pulled by an appropriate amount. For this reason, the gold wire is not pulled with an extra force when forming the loop, and the extra gold wire is not supplied, so that a loop having a stable shape can be obtained. DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram illustrating the principle of an embodiment of a loop forming method according to the present invention. For ease of explanation, the same parts as those in the above-described conventional example are denoted by the same reference numerals. The method of the present invention differs from the conventional loop formation method described above in that a step point 7 is set during the loop-down operation from the loop-up point 4 to the second bond point 6, and this step point 7 is As a relay point, two-stage loop-down operations e and f are performed. That is, according to the method of the present invention, the step point 7 is set at an appropriate position in the middle of the reference arc d formed by the conventional loop-down operation c and inside the reference arc d. The first loop-down operation e is performed between the first and second loop-up points 5 and 5 along a first arc g having a radius r ₁ formed around a first center point C ₁ set arbitrarily. 1 is moved inside the reference arc d, and the second point having a radius r ₂ formed around an arbitrary second center point C ₂ is formed between the step point 7 and the second bond point 3. A second loop-down operation f is performed along the arc h, and the capillary 1 is configured to reach the second bond point 3 from the inside to the outside of the reference arc d. The position of the first center point C ₁ may be a radial position where the loop-up point 5 and the step point 7 can be connected by an arc, and the position of the second center point C ₂ is
The step point 7 and the second bond point 3 may be connected by a circular arc, and the radial position may be such that the circular arc passes from the inside to the second bond point of the reference arc. Thus, step point 7 is sandwiched between 2
When the loop-down operation is performed in stages, the first loop-down operation e from the loop-up point 5 to the step point 7 e
Sometimes, the capillary 1 passes through the inside of the reference arc d, so that the gold wire 5 is not pulled and the bend 6 does not extend, and the second loop-down operation f from the step point 7 to the second bond point 3 f. Sometimes, the capillary 1 moves from the inside to the outside of the reference arc d and reaches the second bond point 3, so that the gold wire 5 can be pulled by an appropriate amount. As a result, the gold wire is not pulled with an extra force when the loop is formed, and the extra gold wire is not supplied. Therefore, as shown in FIG. The loop shape is bent and the saddle 6 remains,
It is possible to obtain a loop having a stable shape in which the gold wire portion following the bend 6 extends linearly. For this reason, a sufficient loop height can be obtained, and at the same time, a sufficient gap can be formed between the gold wire and the chip edge, which can be used for any semiconductor device. In the above example, a gold wire is used as the lead wire, but it goes without saying that the present invention can be similarly implemented even when another metal wire is used. As described above, according to the method of the present invention, the step point is positioned at an appropriate position in the middle of the reference arc connecting the loop-up point and the second bond point and at an appropriate position inside the reference arc. Between the step point and the loop-up point, the reference arc of the reference arc is formed along a first arc connecting the step point and the loop-up point formed around the arbitrarily set first center point. While moving the inside, the second point arbitrarily set between the step point and the second bond point
Since it is made to move from the inside of the reference arc to the second bond point along the second arc connecting the step point formed around the center point and the second bond point, When the loop is formed, the lead wire is not pulled with an extra force, and no extra lead wire is supplied, so that a loop having a stable shape in which the lead wire does not sag can be formed. Therefore, it can be applied to any semiconductor device. Moreover, since the loop shape is stable, the occurrence rate of defective products is reduced, and the production efficiency can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram illustrating the principle of a loop forming method according to the present invention. FIG. 2 is a movement locus diagram of a capillary in a conventional loop forming method. FIG. 3 is a loop shape diagram in the case where the supply amount of the gold wire is about the same as the loop length in the conventional loop forming method. FIG. 4 is a loop shape diagram when the supply amount of the gold wire is longer than the loop length in the conventional loop forming method. [Explanation of Symbols] 1 Capillary 2 First bond point (pad) 3 Second bond point (lead) 4 Leap-up point 5 Gold wire (lead wire) 6 Bending bar 7 Step point 8 Gold wire (lead wire) a Reverse operation b Loop-up operation c Loop-down operation d Reference arc e First loop-down operation f Second loop-down operation g First arc h Second arc C ₁ First center point C ₂ Second center point r ₁ Radius of arc 1 r ₂ radius of second arc

──────────────────────────────────────────────────── ----- Continuation of the front page (56) References JP-A 63-42135 (JP, A) JP-A 4-33346 (JP, A) JP-A 62-140427 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) H01L 21/60

Claims (1)

(57) [Claims] [Claim 1] After bonding a lead wire to the first bond point,
Loop formation of a lead wire in a wire bonding apparatus in which a capillary is pulled up slightly to perform a reverse operation and then pulled up to a loop-up point and then moved along the reference arc from the loop-up point to the second bond point In the method, a step point is set at an appropriate position in the middle of the reference arc connecting the loop-up point and the second bond point, and at an appropriate position inside the reference arc, and an arbitrary interval between the step point and the loop-up point is set. The inside of the reference arc is moved along a first arc connecting the step point and the loop-up point formed with the first center point set to be between the step point and the second bond point. Is a step point formed around an arbitrarily set second center point and the second point.
A method of forming a loop of a lead wire in a wire bonding apparatus, wherein the lead wire is moved along the second arc connecting the bond points from the inside of the reference arc to the second bond point through the outside.